Problems with Measuring voltages

[jerryyu]

I am trying to measure the amounts of voltages that I can get out of dry bones due to their piezoelectric properties. (basically I place the bones in between two copper metal plates with wires taped to the top and bottom of the plates). The problems I encountered was that even without releasing much stresses onto the metal plate i can still get a voltages reading and that number just stay there without me doing anything. And when my hands kind of touches it again, the voltages increased. I went to ask someone and they told me that it might be the static electricity that were built on my hand and that I should touch a metal material before doing the experiment. I did, and the same thing still happen, even after multiple tries. Just what am I doing wrong?? (I also tried putting book in the middle of the metal plates instead,and I was still able to get voltages reading).

[alpha2cen]

How high is the voltage?

[jerryyu]

it's not that much...around .1 volts

[TonyMcC]

If the voltages you are getting are sinusoidal and mains frequency they would be pick up from nearby wiring. You would need a cathode ray oscilloscope to see the waveform shape and determine its frequency.

[John Cuthber]

This bit

"I also tried putting book in the middle of the metal plates instead,and I was still able to get voltages reading"

is interesting.

What sort of voltmeter are you using?

Is it one with a very high input impedance (an electrometer)?